It is known practice to dye keratin fibers, such as human hair, with dye compositions containing oxidation dye precursors, such as ortho- or para-phenylenediamines, ortho- or para-aminophenols, and heterocyclic compounds, which are generally referred to as oxidation bases. These oxidation bases can be colorless or weakly colored compounds which, when combined with oxidizing products, may give rise to colored compounds by a process of oxidative condensation.
It is also known that the shades obtained with these oxidation bases may be varied by combining them with couplers or coloration modifiers, which may be chosen from aromatic meta-diaminobenzenes, meta-aminophenols, meta-diphenols and certain heterocyclic compounds such as indole compounds.
The variety of molecules that can be used as oxidation bases and couplers makes it possible to obtain a wide range of colors.
The “permanent” coloration obtained by means of these oxidation dyes should, moreover, satisfy a certain number of requirements. Thus, it should not have toxicological drawbacks, it may allow shades of the desired intensity to be obtained, and it may have good resistance to external agents such as light, bad weather, washing, permanent waving, perspiration and rubbing.
The dyes may also allow white hairs to be covered, and lastly, they may be as unselective as possible, i.e., they may allow the smallest possible differences in coloration to be produced over the entire length of the same keratin fiber, which is generally differently sensitized (e.g., damaged) between its end and its root.